Microcontroller for ECG (Holter monitor)

Since I have very little previous experience with microcontrollers, I'm looking for an advice on which microcontroller to get that will be appropriate for Holter monitoring (ECG signals from external circuit with 3 channels)? It should be as small as possible with low battery usage (because of for 24 h+ monitoring) and good enough performance for ECG application. As far as connectivity goes, I will use Bluetooth and maybe Wi-Fi, but Bluetooth is crucial for sure. Are there any suitable microcontrollers with Bluetooth integrated or would I have to pair it with external BT module? If that is the case, which combination would you then recommend to me?

Any advise would be greatly appreciated! Thanks

You can get Bluetooth modules with a UART interface which will be compatible with most modern microcontrollers.
Ive been using the HC-05 modules which are really easy to get working but they consume 4mA on standby (20mA transmit/receive).
Look up the HM-10 module for a starting point, I've read that they consume far less power and run on the new 4.0 standard. You can get some with 0.1" headers so they will slot right into a breadboard.

Not too sure about your microcontroller but most smaller PIC's and ATMEL's will consume a low current depending on how fast you clock them.
Most come with sleep mode too.. Depends if you can afford to power down your microcontroller periodically?